1. Field of the Invention
The present invention relates to an opening and closing member control system for controlling movement of an opening and closing member.
2. Description of Related Art
In a case where a power window system of a vehicle is designed to detect pinching of a hard object by a window glass, when a soft object is pinched by the window glass, the pinching of the soft object may not be detected, or the detection of the pinching of the soft object may be delayed. In contrast, in a case where the power window system is designed to detect pinching of the soft object, a threshold value for detecting the pinching is reduced. This will likely cause erroneous detection of the pinching.
In order to address the above disadvantage, for example, Japanese Unexamined Patent Publication No. H07-158338 discloses use of two threshold values, i.e., a threshold value for the hard objects and a threshold value for the soft objects. In Japanese Unexamined Patent Publication No. H07-158338, a change rate of a rotational period is computed based on a pulse signal, which indicates rotation of a motor that drives the window glass. When the change rate of the rotational period exceeds the first threshold value (the threshold value that corresponds to the hard objects), it is immediately determined that the object is pinched by the window glass. When the change rate of the rotational period is decreased below the first threshold value but above a second threshold value (the threshold value that corresponds to the soft objects) through a period of a predetermined number of pulses, it is determined that the object is pinched by the window glass. In this way, the technique recited in Japanese Unexamined Patent Publication No. H07-158338 allows detection of both the hard objects and the soft objects.
However, in the above described technique, when an object of an intermediate hardness between the soft objects and the hard objects is pinched by the window glass, the pinching of the object cannot be detected until the second threshold value, which corresponds to the soft objects, is exceeded continuously a predetermined number of times. Thus, at the time of detecting the pinching of the object, the pinching load is disadvantageously increased, so that detection of the pinched object at a relatively low pinching load is not possible.